Conductive External Connector Structure and Method of Forming

ABSTRACT

External electrical connectors and methods of forming such external electrical connectors are discussed. A method includes forming an external electrical connector structure on a substrate. The forming the external electrical connector structure includes plating a pillar on the substrate at a first agitation level affected at the substrate in a first solution. The method further includes plating solder on the external electrical connector structure at a second agitation level affected at the substrate in a second solution. The second agitation level affected at the substrate is greater than the first agitation level affected at the substrate. The plating the solder further forms a shell on a sidewall of the external electrical connector structure.

BACKGROUND

The semiconductor industry has experienced rapid growth due tocontinuous improvements in the integration density of a variety ofelectronic components (e.g., transistors, diodes, resistors, capacitors,etc.). For the most part, this improvement in integration density hascome from repeated reductions in minimum feature size (e.g., shrinkingthe semiconductor process node towards the sub-20 nm node), which allowsmore components to be integrated into a given area.

This improved integration density has led, in some instances, to smallerintegrated circuit dies. The decrease in size of integrated circuit diescan cause a need for smaller external electrical connectors arranged ina higher density. However, the smaller external electrical connectorsand the higher density of them can result in problems that may havepreviously not been encountered.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIGS. 1 through 4 are cross-sectional views of intermediate steps in themanufacturing of a conductive external connector in accordance with someembodiments.

FIG. 5 is a flow chart of the manufacturing of the conductive externalconnector in accordance with some embodiments.

FIG. 6 is a simplified diagram of a plating system used in accordancewith some embodiments.

FIG. 7 is a cross-sectional view of a first example shielding plate inthe plating system of FIG. 6 in accordance with some embodiments.

FIG. 8 is a cross-sectional view of a second example shielding plate inthe plating system of FIG. 6 in accordance with some embodiments.

FIG. 9 is a cross-sectional view of an example paddle in the platingsystem of FIG. 6 in accordance with some embodiments.

FIG. 10 is an exploded perspective view of an anode module that includesan example shielding plate in the plating system of FIG. 6 in accordancewith some embodiments.

FIG. 11 is a cross-sectional view of an example paddle in the platingsystem of FIG. 6 in accordance with some embodiments.

FIG. 12 is a flow chart for plating in accordance with some embodiments.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the invention. Specificexamples of components and arrangements are described below to simplifythe present disclosure. These are, of course, merely examples and arenot intended to be limiting. For example, the formation of a firstfeature over or on a second feature in the description that follows mayinclude embodiments in which the first and second features are formed indirect contact, and may also include embodiments in which additionalfeatures may be formed between the first and second features, such thatthe first and second features may not be in direct contact. In addition,the present disclosure may repeat reference numerals and/or letters inthe various examples. This repetition is for the purpose of simplicityand clarity and does not in itself dictate a relationship between thevarious embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Embodiments discussed herein may be discussed in a specific context,namely a conductive external connector, such as a pillar with solderthereon, formed on a substrate, such as an integrated circuit die, andmethods of forming such a conductive connector. Other embodimentscontemplate other applications, such as on a package component or thelike, that would be readily apparent to a person of ordinary skill inthe art upon reading this disclosure. It should be noted thatembodiments discussed herein may not necessarily illustrate everycomponent or feature that may be present in a structure. For example,multiples of a component may be omitted from a figure, such as whendiscussion of one of the component may be sufficient to convey aspectsof the embodiment. Further, method embodiments discussed herein may bediscussed as being performed in a particular order; however, othermethod embodiments may be performed in any logical order.

FIGS. 1 through 4 illustrate cross-sectional views of intermediate stepsin the manufacturing of a conductive external connector in accordancewith some embodiments, and FIG. 5 is a flow chart of the manufacturingof the conductive external connector in accordance with someembodiments. The steps of FIG. 5 will be discussed in the context of thecross-sectional views of FIGS. 1 through 4. The conductive externalconnector described in the context of the following illustratedembodiment is a metal pillar with solder on the metal pillar. Otherembodiments can include different pillar structures, differentmaterials, or the like.

In FIG. 1 and in step 100 of FIG. 5, a substrate 50 with a conductivepad 52 exposed through one or more dielectric layer 54 and 56 isprovided. In the illustrated embodiment, the substrate 50 is anintegrated circuit die, which may further be a part of a wafer (e.g.,before singulation). The substrate 50 can include a semiconductorsubstrate, such as a bulk semiconductor substrate, asemiconductor-on-insulator (SOI) substrate, a multi-layered or gradientsubstrate, or the like. The semiconductor of the semiconductor substratemay include any semiconductor material, such as elemental semiconductorlike silicon, germanium, or the like; a compound or alloy semiconductor;the like; or a combination thereof. The semiconductor substrate mayfurther be a wafer, for example, which may further be a bulk siliconwafer. Devices, such as transistors, diodes, capacitors, resistors,etc., may be formed in and/or on the semiconductor substrate, and may beinterconnected by interconnect structures formed by, for example,metallization patterns in one or more dielectric layers on thesemiconductor substrate to form the integrated circuit of the integratedcircuit die.

A conductive pad 52 is on the substrate 50. The conductive pad 52 may beformed over and in electrical contact with the interconnect structure inthe substrate 50 in order to provide an external connection to theintegrated circuit of the integrated circuit die. The conductive pad 52may be on what may be referred to as an active side of the substrate 50(or integrated circuit die). In some embodiments, the conductive pad 52may be formed on, for example, a surface of an uppermost dielectriclayer of the substrate 50. The conductive pad 52 may include a thin seedlayer with a conductive material over the seed layer. The seed layer caninclude copper, titanium, nickel, gold, tin, the like, or a combinationthereof deposited by Physical Vapor Deposition (PVD) or the like. Theconductive material of the conductive pad 52 may be aluminum, copper,tungsten, silver, gold, tin, the like, or a combination thereofdeposited by an electro-chemical plating process, Chemical VaporDeposition (CVD), PVD, Atomic Layer Deposition (ALD), the like, or acombination thereof.

A first dielectric layer 54 is formed on the substrate 50 and over theconductive pad 52 as illustrated in FIG. 1. The first dielectric layer54 (e.g., a passivation layer) may be one or more suitable dielectricmaterials such as silicon oxide, silicon nitride, low-k dielectrics suchas carbon doped oxides, or the like deposited by CVD, PVD, ALD, aspin-on-dielectric process, the like, or a combination thereof. Anopening is formed through the first dielectric layer 54 to expose aportion of the conductive pad 52. The opening may be formed by, forexample, etching, milling, a laser technique, the like, or a combinationthereof.

A second dielectric layer 56 is then formed on the first dielectriclayer 54 and over the conductive pad 52 as illustrated in FIG. 1. Thesecond dielectric layer 56 may be one or more suitable dielectricmaterial, such as a polymer like polyimide, polybenzoxazole (PBO),benzocyclobutene (BCB), the like, or a combination thereof. The seconddielectric layer 56 may be formed through a process such as aspin-on-dielectric process, a lamination process, the like, or acombination thereof. An opening is formed through the second dielectriclayer 56 and through the opening in the first dielectric layer 54 toexpose a portion of the conductive pad 52. The opening may be formed by,for example, etching, milling, laser techniques, exposing the seconddielectric layer 56 to light when the second dielectric layer 56 isphoto-sensitive, the like, or a combination thereof.

An Under Bump Metallurgy (UBM) is then formed on the second dielectriclayer 56, along surfaces of the opening through the second dielectriclayer 56, and on the exposed portion of the conductive pad 52. In someembodiments, the UBM is a metal layer, which may be a single layer or acomposite layer comprising a plurality of sub-layers formed of differentmaterials, and may be deposited using PVD or the like.

In the illustrated embodiment and in step 102 of FIG. 5, the formationof the UBM includes forming an adhesion layer 58 at least on theconductive pad 52. The adhesion layer 58 is formed on the seconddielectric layer 56, along surfaces of the opening through the seconddielectric layer 56, and on the exposed portion of the conductive pad52, as illustrated in FIG. 1. The adhesion layer 58, in someembodiments, is titanium (Ti), titanium tungsten (TiW), or the likedeposited by PVD or the like.

Further in the illustrated embodiment and in step 104 of FIG. 5, theformation of the UBM further includes forming a seed layer 60 on theadhesion layer 58. The seed layer 60, in some embodiments, is copper(Cu) or the like deposited by PVD or the like.

Then in FIG. 1 and in step 106 of FIG. 5, a photoresist 62 is depositedand patterned on the UBM (e.g., on the seed layer 60) as a mask. Thephotoresist 62 may be formed by spin coating or the like and may beexposed to light for patterning. The pattern of the photoresist 62corresponds to a pattern of the conductive external connector that willbe formed. The patterning forms an opening 64 through the photoresist 62to expose the UBM (e.g., the seed layer 60).

In FIG. 2 and in step 108 of FIG. 5, a pillar 66 of the conductiveexternal connector is plated on the UBM (e.g., the seed layer 60) in theopening 64 of the photoresist 62. In some embodiments, the pillar 66 isa metal pillar, which may be copper (Cu), aluminum (Al), nickel (Ni),gold (Au), silver (Ag), palladium (Pd), the like, or a combinationthereof. Additional details of the plating process of step 108 arediscussed in further detail with respect to FIGS. 6 through 12.

Further in FIG. 2 and in step 110 of FIG. 5, optionally, a barrier layer68 of the conductive external connector is plated on the pillar 66 inthe opening 64 of the photoresist 62. In some embodiments, the barrierlayer 68 is a metal layer, which, for example, may reduce or inhibit areaction between solder and the pillar 66 that can form aninter-metallic compound (IMC). In some embodiments, such as when thepillar 66 is copper, the barrier layer 68 is nickel (Ni) or the like.Additional details of the plating process of step 110 are discussed infurther detail with respect to FIGS. 6 through 12. The barrier layer 68can be omitted in some embodiments.

Further in FIG. 2 and in step 112 of FIG. 5, solder 70 of the conductiveexternal connector is plated on the barrier layer 68 in the opening 64of the photoresist 62. In some embodiments, the solder 70 is atin-containing solder, such as having a composition including tin andsilver, or the like. The solder 70 may be a lead-free solder material.In some embodiments, the solder 70 has a composition of tin and silver,where the tin is in a range from about 97.7% to about 98.5% of thesolder composition, and silver is in a range from about 1.5% to about2.3% of the solder composition. In some embodiments, the composition ofthe solder 70 can vary throughout a thickness of the solder 70, such asbecause of different plating speeds of different elements.

By plating the solder 70 in accordance with some embodiments, as will bediscussed in further detail with respect to FIGS. 6 through 12, a shell72 is formed along sidewalls of the barrier layer 68 and/or pillar 66.The shell 72 can be a tin-containing material. In some embodiments, theshell 72 has a composition of tin and silver, where the tin is in arange from about 97.7% to about 98.5% of the shell composition, andsilver is in a range from about 1.5% to about 2.3% of the shellcomposition. In some embodiments, a composition of the shell 72 may havea slightly higher percentage of silver than the composition of thesolder 70, such as because silver can plate to the sidewall of thepillar 66 at a higher rate, such as when the pillar 66 is copper.

In FIG. 3 and in step 114, the photoresist 62 is removed. Thephotoresist 62 can be removed by using any acceptable ashing orstripping process, such as an oxygen plasma ashing, or the like.

Further in FIG. 3 and in step 116, the UBM (e.g., the seed layer 60 andthe adhesion layer 58) is etched to remove portions of the UBM that donot underlie the pillar 66. After removal of the photoresist 62, aportion of the seed layer 60 that is not underlying the pillar 66 willbe exposed. This exposed portion of the seed layer 60 and acorresponding underlying portion of the adhesion layer 58 are etchedusing an appropriate etch process. For example, a wet etch selective tomaterials of the seed layer 60 and the adhesion layer 58, such as ahydrochloric acid (HCl) etch, can be used.

As shown in FIG. 3, the sidewall of the barrier layer 68 and pillar 66can have a first dimension D1 (e.g., a height) from a top surface of theUBM (e.g., the seed layer 60) to a top surface of the barrier layer 68.Further, the shell 72 extends a second dimension D2 from the top surfaceof the barrier layer 68 and along the sidewall of the barrier layer 68and pillar 66. The second dimension D2 can be in a range from about 5%to about 100% of the first dimension D1, such as in a range from about5% to about 10% of the first dimension D1. The shell 72 extends from thetop surface of the barrier layer 68 a distance below an interfacebetween the barrier layer 68 and the pillar 66. In some examples, thefirst dimension D1 is in a range from about 40 μm to about 70 μm, andthe second dimension D2 is in a range from about 1 μm to about 15 μm.

In some embodiments, at least a portion of the UBM (e.g., the seed layer60) and the pillar 66 are the same materials, for example, copper. Inthese embodiments, the etch process to remove exposed portions of theUBM can also etch exposed portions of the pillar 66 below the shell 72.This etching of the pillar 66 can result in an undercut portion 74(identified by the dashed line) of the pillar 66 below the shell 72being removed. During the etching, the shell 72 can protect the pillar66 from being etched where the shell 72 covers the pillar 66.Accordingly, a lower portion of the pillar 66 can have a third dimensionD3 (e.g., width) that is smaller than a fourth dimension D4 (e.g.,width) of an upper portion of the pillar 66. In other embodiments, thepillar 66 is not etched during the etching of the UBM. In some examples,the third dimension D3 is in a range from about 38 μm to about 68 μm,and the fourth dimension D4 is in a range from about 40 μm to about 70μm.

As further shown in FIG. 3, the shell 72 can have a fifth dimension D5(e.g., a thickness) along the sidewalls of the barrier layer 68 and/orpillar 66. A sixth dimension D6 is from an exterior surface of the shell72 of a first side of the external conductive connector to anotherexterior surface of the shell 72 of a second, opposite side of theexternal conductive connector. A seventh dimension D7 is a height of thesolder 70, which may be substantially uniform throughout the solder 70.The fifth dimension D5 can be less than, such as substantially lessthan, the seventh dimension D7. For example, the fifth dimension D5 canin a range from 1% to about 7% of the seventh dimension D7. In someexamples, the fifth dimension D5 is equal to or less than about 1 μm;the sixth dimension D6 is in a range from about 25 μm to about 90 μm;and the seventh dimension D7 is in a range from about 10 μm to about 28μm.

In FIG. 4 and in step 118 of FIG. 5, the solder 70 is reflowed to formreflowed solder 76. The reflow can be performed at any temperaturecapable of adequately melting the solder 70, such as, for example, equalto or greater than 240° C. Surface tension of the solder 70 while meltedduring the reflow step can cause the outer surface of the reflowedsolder 76 to be rounded. In some embodiments, the shell 72 can bereflowed during the reflow process and still remain on sidewalls of thebarrier layer 68 and/or pillar 66. In some embodiments where the solder70 and the shell 72 have a composition of tin and silver, the percentageof silver in each can decrease as a result of the reflow process. Forexample, silver can more readily diffuse into the barrier layer 68and/or pillar 66. As an example, when the solder 70 and shell 72 have acomposition of about 97.7% to about 98.5% of tin and about 1.5% to about2.3% of silver before the reflow, after the reflow the reflowed solder76 and shell 72 can have a composition of about 97.8% to about 98.6% oftin and about 1.4% to about 2.2% of silver. In still furtherembodiments, the reflow process may cause an intermetallic compound(IMC) to be formed in the reflowed solder 76 and the shell 72. The IMCcan be a material formed by a reaction between the material of thesolder 70 and the shell 72 and the material(s) of the barrier layer 68and/or pillar 66. For example, an IMC in the shell 72 can be atin-copper alloy and/or a tin-nickel alloy when the shell 72 istin-silver, the pillar 66 is copper, and the barrier layer 68 is nickel.The IMC in the shell 72 can have a thickness from the sidewall of thepillar 66 that is equal to or greater than about half of the fifthdimension D5.

An eighth dimension D8 is a largest height of the reflowed solder 76.The fifth dimension D5 can be less than, such as substantially lessthan, the eighth dimension D8. For example, the fifth dimension D5 canin a range from 1% to about 5% of the eighth dimension D8. In someexamples, the eighth dimension D8 is in a range from about 15 μm toabout 40 μm.

Although not specifically illustrated, the structure of FIG. 4 mayfurther be bonded to another package component, such as anotherintegrated circuit die, package substrate, or the like. The otherpackage component may include a bond pad to which the reflowed solder 76is attached through reflowing the reflowed solder 76. A dimensionbetween the barrier layer 68 (or the pillar 66 when the barrier layer 68is omitted) and the bond pad of the other package component can begreater than, such as substantially greater than, the fifth dimension D5of the shell 72.

FIG. 6 is a simplified diagram of a plating system used in accordancewith some embodiments. In some embodiments and in some plating steps,the plating system may be an EBARA Model UFP-A from EBARA Corporationheadquartered in Tokyo, Japan. In other embodiments and/or in otherplating steps, the plating system may be a NEXX Model Stratus 300 fromTEL NEXX, Inc. headquartered in the United States.

The plating system includes a tank 200, an anode 202, a substrate holder204, a shielding plate 208, and a paddle 220. In operation, a platingsolution 230 is in the tank 200, and the substrate holder 204 (with thesubstrate 50) and the anode 202 are immersed in the plating solution230. Further, a power supply 206 is coupled between the anode 202 andthe substrate holder 204 such that a current can flow through theplating solution 230 between the anode 202 and the substrate 50 to causea material to be plated on the substrate 50. The shielding plate 208 isdisposed in the tank 200 between the anode 202 and the substrate holder204 and can shield an extraneous electric field to allow plating to bemore uniform on the substrate 50. The paddle 220 can agitate the platingsolution 230 to, at least in part, mix the plating solution 230 to bemore uniform in composition as the plating solution 230 is depleted bythe plating process. The agitation by the paddle 220 may be caused byreciprocating the paddle 220 in direction 222, which is perpendicular tothe top surface of the plating solution 230 (e.g., in a Z-direction), orin direction 224, which is parallel to the top surface of the platingsolution 230 and intersects a flow of electrical current between theanode 202 and the substrate holder 204 (e.g., in an X-direction), inthis example. A ninth dimension D9 is between the anode 202 and thesubstrate holder 204. A tenth dimension D10 is between the substrateholder 204 and the paddle 220. An eleventh dimension D11 is between theshielding plate 208 and the paddle 220. A twelfth dimension D12 isbetween the shielding plate 208 and the anode 202. These dimensions canremain the same or similar between plating steps or can be variedbetween plating steps, as will be discussed subsequently.

The plating system further includes a circulation unit that includes apump 232 with an outlet 234 from the tank 200 and an inlet 236 to thetank 200. The circulation unit can circulate the plating solution 230 inthe tank 200 to, at least in part, mix the plating solution 230 duringthe plating process. The plating system also includes a replenishingreservoir 238 with inlet 240 to the tank 200 and a depleted-solutionreservoir 242 with outlet 244 from the tank 200. The replenishingreservoir 238 can contain a fresh, un-depleted source of the platingsolution 230. The depleted-solution reservoir 242 can contain used,depleted plating solution 230. The depleted-solution reservoir 242 canremove plating solution 230 from the tank 200 via outlet 244, and thereplenishing reservoir 238 can add new plating solution 230 to the tank200 via inlet 240.

FIGS. 7 through 9 illustrate additional details of a plating system,such as an EBARA Model UFP-A. FIGS. 7 and 8 illustrate different exampleshielding plates 208 a and 208 b, respectively, along the cross-sectionA-A in FIG. 6. The shielding plates 208 a and 208 b can be a dielectricmaterial, such as polyvinyl chloride (PVC) or the like. The shieldingplates 208 a and 208 b have an opening 250 a and 205 b, respectively.Each of the openings 250 a and 250 b can have a diameter that is lessthan a diameter of the substrate 50 (e.g., wafer) on the substrateholder 204. FIG. 9 illustrates an example paddle 220 a along thecross-section B-B in FIG. 6. The paddle 220 a can be a metal, such astitanium, coated with Teflon, or the like. The paddle 220 a, asillustrated, is a rectangular shape having vertical slits 260 a (e.g.,extending along a Z-direction). In some embodiments, the paddle 220 aoscillates in direction 224.

FIGS. 10 and 11 illustrate additional details of another plating system,such as a NEXX Model Stratus 300. FIG. 10 illustrates an explodedperspective view of an anode module that includes a shielding plate 208c. The anode module includes, in order along the Y-direction, theshielding plate 208 c, an outer membrane support 262, a membrane 264, aninner membrane support 266, an anode boot 268, the anode 202 with aclamp band around the anode 270, a tensioner 272, an 0 ring 274, and ananode lead rod 276. The anode module further includes an input block 278at a top of the module. FIG. 11 illustrates an example paddle 220 balong the cross-section B-B in FIG. 6. The paddle 220 b can be a metal,such as titanium, coated with Teflon, or the like. The paddle 220 b, asillustrated, is a rectangular shape having horizontal slits 260 n (e.g.,extending along an X-direction). In some embodiments, the paddle 220 boscillates in direction 222.

FIG. 12 illustrates a process flow for plating in accordance with someembodiments. The generic process of FIG. 12 will be discussed first, andthen, implementations of the generic process of FIG. 12 as implementedas each of steps 108, 110, and 112 of FIG. 5 will be discussed. Further,the operation of FIG. 12 will be discussed in the context of the platingsystem(s) of FIG. 6.

In step 300, a substrate 50 on a substrate holder 204 is immersed into aplating solution 230 in a tank 200 having a desired tank arrangement. Instep 302, agitation is turned on to achieve a desired agitation leveland/or condition affected at the substrate 50 on the substrate holder204. The agitation level and/or condition affected at the substrate 50,in some examples, is caused by the paddle 220 reciprocating in direction222 and/or 224 and/or in conjunction with the tank arrangement. In step304, a power supply 206 is turned on to an anode 202 and substrateholder 204. In step 306, a desired material is plated on the substrate50, which is caused by electrical current flowing through the platingsolution 230. Once a desired structure is achieved by plating thematerial, in step 308, the power supply 206 is turned off, and theagitation is turned off in step 310. Further, in step 312, the substrate50 is removed from the plating solution 230.

In a first implementation embodiment of FIG. 5, generally, one or moreplating system(s) that is used for the plating steps 108, 110, and 112have a same or similar arrangement or configuration. A same platingsystem can be used for all of the plating steps 108, 110, and 112, or adifferent plating system can be used for each of the plating steps 108,110, and 112. In this first implementation embodiment, an EBARA ModelUFP-A is used for each of the plating steps 108, 110, and 112. Forexample, in this first implementation embodiment, the dimensions of theplating system, as shown in FIG. 6, used during each of steps 108, 110,and 112 can be as follows: the ninth dimension D9 may be about 90 mm;the tenth dimension D10 may be in a range from about 19 mm to about 20mm, such as about 19 mm; the eleventh dimension D11 may be in a rangefrom about 19 mm to about 20 mm, such as about 19 mm; and the twelfthdimension D12 may be in a range from about 50 mm to about 52 mm, such asabout 52 mm.

Generally, in this first implementation embodiment, the desiredagitation level and/or condition affected at the substrate 50 duringplating step 112 is greater than the desired agitation level and/orcondition affected at the substrate 50 during plating steps 108 and/or110. Generally, in this first implementation embodiment, this greateragitation level and/or condition during plating step 112 is caused byhaving an increased frequency of reciprocation of the paddle 220 duringstep 112 than during steps 108 and/or 110. In some other embodiments,the greater agitation level and/or condition during plating step 112 canbe caused by having an increased magnitude of reciprocation of thepaddle 220, with or without an increased frequency, during step 112 thanduring steps 108 and/or 110.

According to step 108 of FIG. 5, the substrate 50 is immersed (step 300)in a plating solution 230 in a tank 200 to plate the pillar 66. Acopper(II) sulfate (CuSO₄) base copper solution, such as available fromBASF SE, with a copper additive, such as available from Enthone, Inc.,can be used as the plating solution 230 in step 108 when the pillar 66is to be a copper pillar in accordance with some embodiments. Theagitation is turned on (step 302), and the desired agitation levelaffected at the substrate 50 is a low agitation level that can beachieved by turning on the paddle 220 to reciprocate in direction 224 ata frequency of equal to or less than 300 revolutions per minute (RPM),for example. A magnitude of the reciprocation in direction 224 of thepaddle 220 can be in a range from about 50 mm to about 100 mm, such asabout 80 mm. Under these conditions, the power supply 206 is turned on(step 304), and copper is plated (step 306) on the substrate 50 to forma pillar 66 of copper, as illustrated in FIGS. 2 through 4. Othermaterials, solutions, and parameters can be used, as one of ordinaryskill in the art will readily understand. Once the desired material isplated (step 306) and the power and agitation are turned off (steps 308and 310), the substrate 50 is removed from the plating solution 230 forthe step 108 of FIG. 5.

According to optional step 110 of FIG. 5, the substrate 50 is thenimmersed (step 300) in a plating solution 230 in a tank 200, which maybe a different tank (but may be in a same or similar configuration) fromthe tank used in the plating process of step 108, to plate the barrierlayer 68 on the pillar 66. A nickel sulfaminate base nickel solution canbe used as the plating solution 230 in step 110 when the barrier layer68 is to be a nickel layer in accordance with some embodiments. Theagitation is turned on (step 302), and the desired agitation levelaffected at the substrate 50 is a low agitation level that can beachieved by turning on the paddle 220 to reciprocate in direction 224 ata frequency of equal to or less than 300 RPM, for example. A magnitudeof the reciprocation in direction 224 of the paddle 220 can be in arange from about 50 mm to about 100 mm, such as about 80 mm. Theagitation conditions for step 110 may be the same as the agitationconditions used in step 108, and hence, the agitation levels affected atthe substrate 50 for steps 110 and 108 may be the same. Under theseconditions, the power supply 206 is turned on (step 304), and nickel isplated (step 306) on the pillar 66 to form a barrier layer 68 of nickel,as illustrated in FIGS. 2 through 4. Other materials, solutions, andparameters can be used, as one of ordinary skill in the art will readilyunderstand. Once the desired material is plated (step 306) and the powerand agitation are turned off (steps 308 and 310), the substrate 50 isremoved from the plating solution 230 for the step 110 of FIG. 5. Inother embodiments, step 110, and hence, the barrier layer 68, isomitted.

According to step 112 of FIG. 5, the substrate 50 is then immersed (step300) in a plating solution 230 in a tank 200, which may be a differenttank (but may be in a same or similar configuration) from the tanks usedin the plating process of steps 108 and/or 110, to plate the solder 70on the barrier layer 68 (or the pillar 66 when the barrier layer 68 isomitted). A tin/silver solution with a 202 series additive fromMitsubishi Materials Corporation can be used as the plating solution 230in step 112 when the solder 70 is to have a tin-silver composition inaccordance with some embodiments. The agitation is turned on (step 302),and the desired agitation level affected at the substrate 50 is a highagitation level that can be achieved by turning on the paddle 220 toreciprocate in direction 224 at a frequency of equal to or greater than400 RPM, for example. A magnitude of the reciprocation in direction 224of the paddle 220 can be in a range from about 50 mm to about 100 mm,such as about 80 mm. The agitation level affected at the substrate 50 instep 112 is greater than the agitation level affected at the substrate50 in steps 108 and 110. Under these conditions, the power supply 206 isturned on (step 304), and solder 70 and shell 72 are plated (step 306)on the barrier layer 68 and/or pillar 66, as illustrated in FIGS. 2through 4. Other materials, solutions, and parameters can be used, asone of ordinary skill in the art will readily understand. Once thedesired material is plated (step 306) and the power and agitation areturned off (steps 308 and 310), the substrate 50 is removed from theplating solution 230 for the step 110 of FIG. 5.

In a second implementation embodiment of FIG. 5, generally, a platingsystem that is used for the plating step 112 has different arrangementor configuration from one or more plating system(s) that is used for theplating steps 108 and/or 110. A same plating system can be used for theplating steps 108 and 110, and a different plating system can be usedfor the plating step 112. A different plating system can be used foreach of the plating steps 108, 110, and 112. In this secondimplementation embodiment, an EBARA Model UFP-A is used for each of theplating steps 108 and 110, and a NEXX Model Stratus 300 is used for theplating step 112. For example, in this second implementation embodiment,the dimensions of the plating systems, as shown in FIG. 6, used duringsteps 108 and 110 can be as follows: the ninth dimension D9 may be about90 mm; the tenth dimension D10 may be in a range from about 19 mm toabout 20 mm, such as about 19 mm; the eleventh dimension D11 may be in arange from about 19 mm to about 20 mm, such as about 19 mm; and thetwelfth dimension D12 may be in a range from about 50 mm to about 52 mm,such as about 52 mm. Further, for example, in this second implementationembodiment, the dimensions of the plating systems, as shown in FIG. 6,used during step 112 can be as follows: the ninth dimension D9 may beabout 41 mm; the tenth dimension D10 may be in a range from about 4 mmto about 6 mm, such as about 5 mm; the eleventh dimension D11 may be ina range from about 13 mm to about 23 mm, such as about 18 mm; and thetwelfth dimension D12 may be in a range from about 13 mm to about 23 mm,such as about 18 mm.

Generally, in this second implementation embodiment, the desiredagitation level and/or condition affected at the substrate 50 duringplating step 112 is greater than the desired agitation level and/orcondition affected at the substrate 50 during plating steps 108 and/or110. Generally, in this second implementation embodiment, this greateragitation level and/or condition during plating step 112 is caused byhaving the paddle 220 closer to the substrate 50 and/or reciprocate in adifferent direction during step 112 than during steps 108 and/or 110.

According to step 108 of FIG. 5, the substrate 50 is immersed (step 300)in a plating solution 230 in a tank 200 to plate the pillar 66. The tank200 in this step 108 can have the arrangement and configuration asdiscussed above with respect to step 108 of this second implementationembodiment. A copper(II) sulfate (CuSO₄) base copper solution, such asavailable from BASF SE, with a copper additive, such as available fromEnthone, Inc., can be used as the plating solution 230 in step 108 whenthe pillar 66 is to be a copper pillar in accordance with someembodiments. The agitation is turned on (step 302), and the desiredagitation level affected at the substrate 50 is a low agitation levelthat can be achieved by turning on the paddle 220 to reciprocate indirection 224 (e.g., parallel to the top surface of the plating solution230 and intersecting the flow of current in the solution 230 in anX-direction) at a frequency, such as in a range from about 240 RPM toabout 420 RPM, and more particularly, such as about 350 RPM, forexample. A magnitude of the reciprocation in direction 224 of the paddle220 can be in a range from about 290 mm to about 310 mm, such as about300 mm. Under these conditions, the power supply 206 is turned on (step304), and copper is plated (step 306) on the substrate 50 to form apillar 66 of copper, as illustrated in FIGS. 2 through 4. Othermaterials, solutions, and parameters can be used, as one of ordinaryskill in the art will readily understand. Once the desired material isplated (step 306) and the power and agitation are turned off (steps 308and 310), the substrate 50 is removed from the plating solution 230 forthe step 108 of FIG. 5.

According to optional step 110 of FIG. 5, the substrate 50 is thenimmersed (step 300) in a plating solution 230 in a tank 200, which maybe a different tank (but may be in a same or similar configuration) fromthe tank used in the plating process of step 108, to plate the barrierlayer 68 on the pillar 66. The tank 200 in this step 110 can have thearrangement and configuration as discussed above with respect to step110 of this second implementation embodiment. A nickel sulfaminate basenickel solution can be used as the plating solution 230 in step 110 whenthe barrier layer 68 is to be a nickel layer in accordance with someembodiments. The agitation is turned on (step 302), and the desiredagitation level affected at the substrate 50 is a low agitation levelthat can be achieved by turning on the paddle 220 to reciprocate indirection 224 (e.g., parallel to the top surface of the plating solution230 and intersecting the flow of current in the solution 230 in anX-direction) at a frequency, such as in a range from about 240 RPM toabout 420 RPM, and more particularly, such as about 300 RPM, forexample. A magnitude of the reciprocation in direction 224 of the paddle220 can be in a range from about 290 mm to about 310 mm, such as about300 mm. The agitation conditions for step 110 may be the same as theagitation conditions used in step 108, and hence, the agitation levelsaffected at the substrate 50 for steps 110 and 108 may be the same.Under these conditions, the power supply 206 is turned on (step 304),and nickel is plated (step 306) on the pillar 66 to form a barrier layer68 of nickel, as illustrated in FIGS. 2 through 4. Other materials,solutions, and parameters can be used, as one of ordinary skill in theart will readily understand. Once the desired material is plated (step306) and the power and agitation are turned off (steps 308 and 310), thesubstrate 50 is removed from the plating solution 230 for the step 110of FIG. 5. In other embodiments, step 110, and hence, the barrier layer68, is omitted.

According to step 112 of FIG. 5, the substrate 50 is then immersed (step300) in a plating solution 230 in a tank 200, which may be a differenttank (and has a different configuration) from the tanks used in theplating process of steps 108 and/or 110, to plate the solder 70 on thebarrier layer 68 (or the pillar 66 when the barrier layer 68 isomitted). The tank 200 in this step 112 can have the arrangement andconfiguration as discussed above with respect to step 112 of this secondimplementation embodiment. The dimensions D9, D10, D11, and D12 of thetank 200 used for step 112 are less than the dimensions D9, D10, D11,and D12, respectively, of the tank 200 used for step(s) 108 and/or 110.A tin/silver solution with a 202 series additive from MitsubishiMaterials Corporation can be used as the plating solution 230 in step112 when the solder 70 is to have a tin-silver composition in accordancewith some embodiments. The agitation is turned on (step 302), and thedesired agitation level affected at the substrate 50 is a high agitationlevel that can be achieved by turning on the paddle 220 to reciprocatein direction 222 (e.g., perpendicular to the top surface of the platingsolution 230 in a Z-direction) at a frequency, such as in a range fromabout 240 RPM to about 420 RPM, and more particularly, such as about 300RPM, for example. The direction 224 of the reciprocation of the paddle220 in the tank 200 used for step 112 is different from the direction222 of the reciprocation of the paddle 220 in the tank 200 used forstep(s) 108 and/or 110. The frequency of the reciprocation in steps 108,110, and 112 can be equal. A magnitude of the reciprocation in direction224 of the paddle 220 can be in a range from about 50 mm to about 200mm, such as about 150 mm. The magnitude of the reciprocation in steps108, 110, and 112 can be equal. The agitation conditions for step 112may cause greater agitation affected at the substrate 50 than theagitation caused by the conditions used in steps 108 and/or 110. Underthese conditions, the power supply 206 is turned on (step 304), andsolder 70 and shell 72 are plated (step 306) on the barrier layer 68and/or pillar 66, as illustrated in FIGS. 2 through 4. Other materials,solutions, and parameters can be used, as one of ordinary skill in theart will readily understand. Once the desired material is plated (step306) and the power and agitation are turned off (steps 308 and 310), thesubstrate 50 is removed from the plating solution 230 for the step 110of FIG. 5.

Although discussed in different implementation embodiments above, otherembodiments contemplate an increased agitation level affected at thesubstrate 50 during step 112 relative to that in steps 108 and/or 110using an combination of features discussed above, such as anycombination of two or more of increase reciprocation frequency,increased reciprocation magnitude, closer proximity of components, anddifferent reciprocation direction, or other parameter or factor that canaffect an increased agitation level.

By increasing the agitation level affected at the substrate 50 in step112, the photoresist 62 that is used during step 112 can flex or bend tocreate a gap between the photoresist 62 and the pillar 66 and/or barrierlayer 68 during the plating (step 306) to allow the formation of theshell 72. A desired second dimension D2 that the shell 72 extends alonga sidewall can be achieved by a dwell time during the plating in step112. For example, a small dwell time can result in a small dimension D2,and a longer dwell time, such as 120 seconds, can result in a dimensionD2 that nears the dimension D1.

The shell 72 can protect the barrier layer 68 and/or pillar 66 during asubsequent etch step, such as step 116 of FIG. 5 where the seed layer 60and the adhesion layer 58 are etched, to prevent the surface on whichthe solder 70 is plated from being etched away. Hence, the surfaceunderlying the solder 70 can remain supporting the solder 70 during asubsequent reflow process, and the solder 70 can be less prone tocollapsing down on a sidewall of the pillar 66, for example. This can,in some embodiments, allow for higher density layouts of externalconductive connectors that include a pillar with solder. Further, theshell 72 can protect the pillar 66 and/or barrier layer 68 fromoxidizing due to subsequent processing. Also, the shell 72 can protectan interface between the pillar 66 and the barrier layer 68 frommoisture that could otherwise penetrate in the interface. Hence, theshell 72 can increase the reliability of the structure.

An embodiment is a method. The method includes forming an externalelectrical connector structure on a substrate. The forming the externalelectrical connector structure includes plating a pillar on thesubstrate at a first agitation level affected at the substrate in afirst solution. The method further includes plating solder on theexternal electrical connector structure at a second agitation levelaffected at the substrate in a second solution. The second agitationlevel affected at the substrate is greater than the first agitationlevel affected at the substrate. The plating the solder further forms ashell on a sidewall of the external electrical connector structure.

Another embodiment is a method. A pillar is plated on a substrate usinga first plating system. The pillar is at least a part of an externalelectrical connector structure. The first plating system comprises afirst paddle, and the first paddle is reciprocated at a first frequencyin a first plating solution during the plating the pillar. Solder isplated on the external electrical connector structure using a secondplating system. The second plating system comprises a second paddle, andthe second paddle is reciprocated at a second frequency in a secondplating solution during the plating the solder. The second frequency isgreater than the first frequency. The plating the solder further forms ashell along a sidewall of the external electrical connector structure.

Another embodiment is a semiconductor device. A semiconductor devicecomprises a conductive pillar located over a conductive member over asubstrate. A reflowable material is located over the conductive pillar,wherein the reflowable material further comprises a first portionlocated over a first surface of the conductive pillar, wherein the firstsurface faces away from the conductive member, wherein the first portionhas a first concentration of a first component. The reflowable materialalso comprises a second portion located adjacent to but not fullycovering a second surface of the conductive pillar, wherein the secondsurface extends from the first surface towards the substrate, whereinthe second portion has a second concentration of the first componentgreater than the first concentration.

A further embodiment is a method. An under bump metallurgy (UBM) isformed on a substrate. A mask is formed on the UBM, and an openingthrough the mask exposes a portion of the UBM. A pillar is plated on theUBM in the opening through the mask, and the pillar is part of anexternal electrical connector. A solder is plated on the externalelectrical connector. The plating the solder further comprises causingthe mask to flex causing a gap between the mask and a sidewall of theexternal electrical connector. A shell is formed along the sidewall ofthe external electrical connector and between the mask and the sidewallof the external electrical connector in the gap.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

1. A method comprising: forming an external electrical connector structure on a substrate, the forming the external electrical connector structure comprising plating a pillar on the substrate at a first agitation level affected at the substrate in a first solution; and plating solder on the external electrical connector structure at a second agitation level affected at the substrate in a second solution, the second agitation level affected at the substrate being greater than the first agitation level affected at the substrate, the plating the solder further forming a shell on a sidewall of the external electrical connector structure.
 2. The method of claim 1, wherein the forming the external electrical connector structure further comprises plating a barrier layer on the pillar at the first agitation level at the substrate in a third solution.
 3. The method of claim 2, wherein the shell is formed on a sidewall of the barrier layer and on a sidewall of the pillar.
 4. The method of claim 1, wherein the plating the pillar is performed in a first plating system, the first plating system comprising a first paddle, the plating the pillar comprising reciprocating the first paddle in the first solution to cause the first agitation level affected at the substrate, and wherein the plating the solder is performed in a second plating system, the second plating system comprising a second paddle, the plating the solder comprising reciprocating the second paddle in the second solution to cause the second agitation level affected at the substrate.
 5. The method of claim 4, wherein the first paddle is reciprocated at a first frequency, and the second paddle is reciprocated at a second frequency greater the first frequency.
 6. The method of claim 5, wherein the first paddle is at a first distance from the substrate during the plating the pillar, and the second paddle is at a second distance from the substrate during the plating the solder, the second distance being equal to the first distance.
 7. The method of claim 4, wherein the first paddle is at a first distance from the substrate during the plating the pillar, and the second paddle is at a second distance from the substrate during the plating the solder, the second distance being less than the first distance.
 8. The method of claim 7, wherein the first paddle is reciprocated at a first frequency, and the second paddle is reciprocated at a second frequency equal to the first frequency.
 9. The method of claim 7, wherein the first paddle is reciprocated along a first direction with respect to the substrate, and the second paddle is reciprocated along a second direction with respect to the substrate, the second direction being different from the first direction.
 10. The method of claim 7, wherein the first paddle is reciprocated along a first direction with respect to the substrate, and the second paddle is reciprocated along a second direction with respect to the substrate, the second direction being perpendicular to the first direction.
 11. The method of claim 1 further comprising reflowing the solder, the shell remaining on the sidewall of the external electrical connector structure after the reflowing.
 12. The method of claim 11, wherein the shell includes an intermetallic compound (IMC) after the reflowing.
 13. The method of claim 1 further comprising: forming an under bump metallurgy (UBM) on the substrate, the pillar being plated on the UBM on the substrate; and after the plating the solder, etching a portion of the UBM while the shell is on the sidewall of the external electrical connector structure.
 14. The method of claim 13, wherein the etching further etches a portion of the pillar, a first width of the pillar proximate the substrate is less than a second width of the pillar distal from the substrate.
 15. A method comprising: plating a pillar on a substrate using a first plating system, the pillar being at least a part of an external electrical connector structure, the first plating system comprising a first paddle, the first paddle being reciprocated at a first frequency in a first plating solution during the plating the pillar; and plating solder on the external electrical connector structure using a second plating system, the second plating system comprising a second paddle, the second paddle being reciprocated at a second frequency in a second plating solution during the plating the solder, the second frequency being greater than the first frequency, the plating the solder further forming a shell along a sidewall of the external electrical connector structure.
 16. The method of claim 15, wherein the first frequency is equal to or less than 300 revolutions per minute (RPM), and the second frequency is equal to or greater than 400 RPM.
 17. The method of claim 15 further comprising: forming an under bump metallurgy (UBM) on the substrate, the pillar being plated on the UBM on the substrate; after the plating the solder, etching a portion of the UBM while the shell is on the sidewall of the external electrical connector structure; and after the etching, reflowing the solder, the shell remaining on the sidewall of the external electrical connector structure after the reflowing.
 18. A method comprising: forming an under bump metallurgy (UBM) on a substrate; forming a mask on the UBM, an opening through the mask exposing a portion of the UBM; plating a pillar on the UBM in the opening through the mask, the pillar being part of an external electrical connector; and plating a solder on the external electrical connector, the plating the solder further comprising causing the mask to flex causing a gap between the mask and a sidewall of the external electrical connector, a shell being formed along the sidewall of the external electrical connector and between the mask and the sidewall of the external electrical connector in the gap.
 19. The method of claim 18, wherein the plating the solder comprises using a first agitation level affected at the substrate greater than a second agitation level affected at the substrate of the plating the pillar, the first agitation level affected at the substrate causing the mask to flex. 20.-22. (canceled)
 23. A method of manufacturing a semiconductor device, the method comprising: forming a conductive pillar located over a conductive member over a substrate; placing a reflowable material located over the conductive pillar, wherein the placing the reflowable material further comprises: placing a first portion located over a first surface of the conductive pillar, wherein the first surface faces away from the conductive member, wherein the first portion has a first concentration of a first component; and placing a second portion located adjacent to but not fully covering a second surface of the conductive pillar, wherein the second surface extends from the first surface towards the substrate, wherein the second portion has a second concentration of the first component greater than the first concentration.
 24. The method of claim 20, wherein the first component is silver.
 25. The method of claim 20, wherein the conductive pillar has a first width at a first point covered by the reflowable material and a second width less than the first width at a second point not covered by the reflowable material, wherein the first width is parallel to a major surface of the substrate. 